Contact system



Dec.,30, 1969 Filed March 13, 1968 P. WILD! CONTACT SYSTEM 3 Sheets-Sheet 1 B F G. l y l5 l0 L H POWER CAPACITOR SUPPLY BANK rem/1110110110011 .\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\v 'IIIIII IIIIIIIIIIIIA FIGS ACTUATOR INVENTOIZ h ap/ five/ im, dials/6a, 10m

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Dec. 30, 1969 Filed March 15, 1968 ATTYS,

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United States Patent 3,487,456 CONTACT SYSTEM Paul Wildi, San Diego, Calif., assignor to Gulf General Atomic Incorporated, San Diego, Calif., a corporation of Delaware Filed Mar. 13, 1968, Ser. No. 712,777 Int. Cl. H01h 3/20 U.S. Cl. 200-166 23 Claims ABSTRACT OF THE DISCLOSURE A contact system includes a plurailty of conductor elements which couple together a set of contacts, and which have a large force applied thereto. The force is applied to the conductor elements through a hydrostatic or quasihydrostatic member, providing a uniform and equal pressure distribution on the plurality of conductor elements.

The present invention relates to high current contact systems for switches and particularly to such systems of the type having multiple contacts at a single pole.

The serious difficulties encountered in mechanically switching and interconnecting high current circuits have long been known and many types of switch contact constructions have heretofore been proposed, each being designed to overcome the various problems involved. These problems are especially acute in magnetic pulse forming apparatus, although certainly not limited thereto, wherein certain of the circuits and transfer switches therein employed maybe subjected to an extremely high surge current duty. Such apparatus, useful in metal working, may generally comprise a capacitor bank capable of storing an extremely large amount of energy which must be delivered as a relatively short pulse to a magnetic forming coil which shapes, forms or otherwise exerts a force on a metal workpiece disposed within the magnetic field produced by the pulse of energy. The conduction of such a curent surge places exceptional requirements on the transfer switch contacts which may be employed, for example, for selectively coupling and uncoupling a number of coils to the capacitor bank and suitable firing or switching means, such as an ignitron, thyratron, etc., which then controls the discharge through the selected coil. When the capacitor bank is discharged, the high current surges pass through the previously engaged contacts of the appropriate transfer switch.

Certain general design considerations for high current contacts which are subjected to extreme magnetic and thermal stresses whenever they conduct a current surge have been heretofore known. More particularly, it has long been known that the actual contact area between two metallic bodies being pressed against each other is only a very small fraction of the apparent contact area because of the actual irregular nature of the surface geometry of the contacting parts. Thus, the current densities at the actual contact points are extremely high. It has also been known that the-higher the contact force applied, the lower the amount of heat generated at the contact points. Also, it has been known that the magnetic forces produced by the current surge decrease with increasing contact force, since this produces a greater number of contact points of larger conducting area,

Based on these well known principles of design, switching contacts have been constructed which provide as many contact points as possible, with the highest possible contact pressure. Contact structures on heretofore existing switch gear are normally divided into individual contact fingers or points, each having only a relatively small contact area but in the aggregate providing the total current carrying capacity required for any specific switching application. These contact fingers are generally individually and discretely spring biased to assure maximum contact pressure and to attempt to-obtain an even distribution of the current over the contacts.

However, such a switch contact construction, when subjected to the extreme conditions hereinbefore mentioned, has a relativel short life in that the contacts deteriorate and malfunction with a total operating time far less than can be considered practical or optimum in various apparatus and applications for general industrial purposes.

The basis underlying these problems of contact failure is essentially one of heat-flow balance at each of the contact points. Since only a relatively small volume of metal on both sides of each contact point carries the very high current density during the passage of a current surge, only a small fraction of the heat generated in this volume will be quickly dissipated to the outlying areas of the contact. Since the bulk or majority of the heat will remain stored in these localized volumes, the material around the contact points may soften, or possibly melt, weld, and/or spatter, the latter effect being due in part to the influence of the magnetic forces produced. Although the utilization of extremely high contact pressures will reduce these effects, this is also limited, because excessively high pressures will result in mechanical deterioration and excessive wear on the contacts. Also, in such existing switch constructions as previously mentioned, it is impractical, if not impossible, to maintain each contact finger at the same and optimum pressure. Therefore, deterioration of the contacts generally results because of either of these conditions, produced with respect to some contacts by insufficient contact pressure, and with respect to others by excessive contact pressure.

In an attempt to provide a uniform pressure over a plurality of contact fingers, it has heretofore been proposed that a plurality of discrete springs be utilized to bias the fingers into switching engagement, and a relatively thin resilient mat be interposed between the springs and the fingers. This type of arrangement, however, still employs the discrete spring concept, and thus does not achieve the pressure uniformity required.

It is a general object of the present invention to provide an improved high surge-current contact system having multiple parallel contact points with provision for producing a uniform current distribution over each of the contact points to provide long operating life and maximum switching effectiveness.

It is a further object of the present invention to provide an improved switch construction having multiple contact points with equally distributed forces over each of the contact points, producing a single uniform contact pressure over the entire aggregate contact area to provide low, equal and uniform contact resistance at each contact point, as well as low inductance.

It is another object of the present invention to provide an improved switch having an actuator mechanism which produces an extremely large contact pressure, but which moves the switching contacts into engagement by applying only relatively little force.

These and other objects of the invention, are more particularly set forth in the following detailed description and in the accompanying drawings, of which:

FIGURE 1 is a highly schematic and simplified diagram of magnetic forming apparatus of the type in which the switch according to the present invention is advantageously employed;

FIGURE 2 is an isometric view generally showing a 7 switch contact assembly in accordance with one embodiment of the present invention;

FIGURE 3 is a view in vertical section taken along the line 3-3 in FIGURE 2, with the contact actuator mechanism shown in block form;

' FIGURE 4 is a view in section showing a movable contact assembly in accordance with another embodiment of the invention;

FIGURES 5 and 6 are views in section showing a movable contact assembly in accordance with further embodiments of the invention;

FIGURE 7 is a more or less schematic view in elevation showing a contact actuator mechanism in accordance with the invention, the alternate extreme positions of the mechanism being shown in solid and dotted line;

FIGURE 8 is a view in longitudinal section showing a contact assembly in accordance with another embodiment of the invention;

FIGURE 9 is a partial transverse sectional view taken along the line 99 in FIGURE 8; and

FIGURE 10 is a view in longitudinal section showing a contact assembly in accordance with still another embodiment of the invention.

Referring now to FIGURE 1, there is generally shown a simplified schematic diagram of an electrical system which may be employed in magnetic forming apparatus, wherein a power supply 10 may charge the capacitor bank 12 of high energy storage capacity through switching means 13 of any suitable type. The energy stored in the capacitor bank 12 may then be selectively delivered to a magnetic forming coil 14a, or to a like or similar coil 14b, by suitable switching or firing means 15 through one or the other of the transfer switches 16a and 16b. The switching or firing means 15 may comprise an ignitron, thyratron, or other high current switching device. The selective coupling to the coils is achieved by engaging the bridging contacts of the desired transfer switches 16a or 16b with their respective associated sets of contacts 17 and 18, by which either of the coils 14a or 14b are connected across the capacitor bank and firing means. The bridging contacts are engaged by suitable driving means 20a and 20b as will be hereinafter discussed.

After the capacitor bank is connected to the power supply 10 and charged, the switch 13 is opened and the switching means 15 is closed by suitable control circuitry (not shown). This discharges the capacitor bank through the bridging contacts of the engaged transfer switch and produces a sudden high intensity current pulse or surge through the selected electromagnetic forming coil (illustrated as 14a), and the current returns to the capacitor bank through a common return conductor. This discharge current-pulse through the coil 14a produces a magnetic field, characterized by the geometry of the coil and its related parts, which in the example illustrated, applies an extremely high compressive force on a metallic collar 26 concentrically disposed about the workpiece 27 in the coil aperture 28, causing the swaging of the collar 26 onto the workpiece 27 in a known manner.

In this way, for example, a single magnetic forming machine may work both ends of a shaft, by first firing the bank into one coil, operating on one end, and then firing the same bank into the other coil, operating on the other end.

A contact system in accordance with an embodiment of the present invention is illustrated in FIGURE 2, which may be advantageously employed as the transfer switches 16 of FIGURE 1, or in other and diverse applications where high current surges are handled. In general, a contact assembly 30 having a plurality of conductor elements 31 is movable relative to a stationary assembly, indicated generally as34, having a set of contacts 46 and 48, and is driven from a switch open position (as shown) to a closed position, in the direction of the arrows, by a driving means or actuator 33', shown schematically in FIGURE 3. The contact assembly 30 comprises forcedistributing means, illustrated as inclluding a rigid contact holder or case 36, responsive to the closure force produced by the driving means, and pressure means 38 responsive to the force-distributing means for providing hyd at s-lilss srs s e on the pl a i y of co d c elements 31, thereby applying an equal pressure to each element so that equalization of Contact resistance is produced at each contact point when the plurality of conductor elements 31 are in engagement with the contacts 46 and 48. The pressure means 38, various preferred embodiments of which are described in detail hereinafter, may comprise an elastomeric cushion as Shown in FIG- URE 3, or, for example, may be in the forms illustrated in, but not limited to, FIGURES 4 through 6.

More particularly, the plurality of conductor elements 31 are formed from a large number of relatively thin contact blades which are arranged in an adjacent or laminar manner, and are generally T-shaped, having an inner portion 40 disposed within the cavity of the holder 36 and an outer portion 42 protruding therefrom. Each of the contact blades 31 are movable relative to each other and to the holder 36, and each presents an outer edge 44a, 44b, 440, etc., the extreme outer end portions of which form contact points with the opposite contact members 46 and 48 of the stationary contact set. The pressure element or cushion 38 is disposed within the holder 36 and is confined thereby between the inwardly facing edges of the blade portions 40 and the inner surfaces of the cavity of the holder 36 so that a substantially high force is applied to substantially all of the cushion area in the direction producing contact engagement.

The stationary assembly 34 is formed by the forward conductor 45 which is switched betwen the contact points 46 and 48, and the return conductor 49. The two conductors 45 and 49 are in the form of plates or planar members which are generally coextensive with the total width across the contact blades 31 and are separated by a layer or sheet of insulation 52. Consequently, this planar assembly provides an extremely small inductance, which is desirable in surge current discharge systems of the type used in magnetic pulse forming apparatus, since any substantial inductance constitutes a substantial impedance to the high current pulses involved.

When the contact assembly 30 is driven toward the contacts 46 and 48 to provide a short circuit thereacross, the contact blades 31 are engaged therewith by a relatively high pressure applied in the direction theretowards by the holder 36 acting through the pressure element 38, the holder 36 being driven by the actuating mechanism 33, described hereinafter. A uniform pressure distribution is provided across each and every one of the contact blades 31 so that each of the contact points formed between the contact portions of edges 44a, 44b, etc., and the contacts 46 and 48 have equal contact resistance. Since each contact blade is independently movable with respect to the others, and since the pressure is everywhere substantially equal, equalization of contact resistance occurs generally regardless of the state of wear of the contacts.

More specifically, with reference now to FIGURE 3, the internal structure of the contact assembly 30 is shown in section, and as being driven by an actuator 33 through a mechanical link 56. The actuator and link mechanism, not shown here in detail, may be any suitable hydraulic or electrical mechanism for driving a system of levers capable of advancing the contact assembly30 to the left (as shown), so that the contact blades 31 create a conductive bridge across the stationary contacts 46 and 48. The pressure element 38 is here specifically shown as a cushion of an elastomeric materiahsuch as rubber or rubber-like plastic, which utilizes the principle that such a material acts similarly to a fluid in producing a quasi-hydrostatic or hydrostatic-like pressure distribution when it, itself, is placed under a high pressure or compressive force. Such an elastomer 38 of rectangularly solid or parallelepiped configuration is confined by the inner walls or cavity of the holder 36 and the inner edges 58 of the contact blades 31. Consequently, when sutficient force is applied to the holder 36, the force is distributed over the inner rear wall 60 of the cavity, and transmitted from the contact; holder 9 h b ad s 3 p odu ng he un form meshes? cal force-field distribution described. The elastomeric material used for the cushion 38 should generally be as soft as possible to yield the best hydrostatic properties, and should desirably have substantial thickness.

Although the inner edges 58 of the blades 31 and the inner wall 60 of the holder 36 are not necessarily bonded to the elastomeric cushion 38, it may be desirable in some instances to have the cushion vulcanized or bonded directly to these parts.

In some constructions, in accordance with the invention, where the nature or properties of the elastomer are such that there may be a tendency to extrude through the contact blades 31 due to the high pressure involved, an elastomeric cushion formed as a sandwich or multiple layer structure of several elastomers of varying hardnesses may be utilized, as shown by the cushion 38a in FIGURE 4, wherein corresponding elements are otherwise indicated by the same reference numerals. More particularly, the elastomeric cushion 38a has a first layer 62 disposed adjacent the edges 58 of the contact blades 31 and is composed of a relatively hard elastomer which is resistant to extrusion, and a layer 64, filling the remainder of the cavity, and composed of a relatively soft elastomer. The ratio of the thicknesses of the hard layer to that of the soft layer is desirably made as small as practical, and yet sufliciently high so as to retain the anti-extrusion properties of the harder material; thus, substantial thickness of the relatively soft elastomer assures the desired high degree of pressure equalization.

A further modification or implementation of the pressure element is shown in FIGURE 5 as 38b. In this embodiment, good pressure equalization may be obtained by utilizing a hydrostatic chamber comprising a flexible or resilient vessel or container 66 filled with a relatively incompressible liquid 68, such as water or oil. The container 66 forms a resilient wall in engagement with the blades 31 and transmits the applied force thereto. The uniform pressure distribution, however, may be limited to some extent by unequal pressure distributions at the peripheral regions of the container 66. However, these peripheral effects may be minimized by the use of a homogeneous and isotropic material for the vessel construction and by minimizing the peripherally affected region as compared to the central region as regards relative area. The utilization of a fluid produces precise equalization of the pressure distribution over a relatively large area because of the relative lack of internal friction in the fluid medium 68.

A further embodiment is shown in FIGURE 6, which is somewhat similar to that shown in FIGURE 5 in that the hydrostatic pressure element 38c is formed by a hydrostatic chamber filled with a like liquid, but the resilient vessel 66 has now been eliminated. In this embodiment, the housing 36 is formed as two separate elements 70 and 72 which are fastened together at the outer periphery by suitable fasteners, clamping therebetween a flexible or resilient wall or diaphragm 74. The diaphragm 74 is suspended from its peripherally clamped portion by an isolating provision or bend 76 so that the force applied at 56 is transmitted uniformly to the blades 31, which are engaged by the diaphragm, with a uniform pressure distribution produced by the action of the incompressible fluid 78 in the chamber defined by the diaphragm 74 and the inner walls 60 of the holder.

Referring now to FIGURE 8, there is shown a further embodiment in accordance with the present invention wherein the contact fingers are arranged in a circular cluster. In particular, the contact assembly comprises a vertically movable contact holder 200 having a circular cylindrical male contact structure 202 fixed to a plate 203 and extending downwardly therefrom. The circular contact structure 202 has a cluster of contact fingers 204 separated by slits 206, as shown in FIGURE 9, the structure being similar to a collet chuck. A stationary contact is formed by a cylindrical bore 208 disposed within a metal member 210. The cavity within the cylindrical male contact structure 202 is filled with a rubber-like elastomer 212, and a rigid plunger or piston 214 is arranged to pr trude through an aperture 216 provided in the movable contact holder plate 203, to engage the elastomer 212 and to distribute thereto, at the surfaces 218, the force applied to the plunger 214. In the embodiment shown, this force is applied downwardly, and may be produced by any suitable means, but the distributed force applied Within the elastomer 212 produces a quasi-hydrostatic pressure which forces the fingers 204 outward and into contact with the cylindrical wall 208 of the stationary contact 210. The movable contact holder 200, and its associated parts, may be moved with relation to the stationary contact 210 by any suitable mechanism so that the cylindrical male contact 202 is received by the cylindrical bore 208. This mechanism may be either separate from the force producing means associated with the plunger 214 or may form a part thereof. Alternatively, the plunger 214 may be replaced by a cavity and line adapted to receive a pressurized fluid for applying sufficient pressure within the elastomeric material 212 to produce the quasi-hydrostatic pressure distribution hereinbefore described. In order to achieve this type of pressure distribution, the elastomeric material 212 should desirably completely fill the cavity within the cylindrical contact structure 202 so that it is entirely confined, and have a volume and radius of sufiicient dimension so as to produce this result. Of course, the elastomeric material .212 may comprise an outer layer or band of harder material than the interior, so as to prevent extrusion through the slits 206 between the fingers 204 of the cylindrical contact structure 202.

Feferring now to FIGURE 10, another embodiment is shown wherein a circular cluster of contact fingers is employed, but in this embodiment, the contact fingers 200 form the stationary contact and a solid rod 222 forms the movable contact member which is adapted to engage with the circular female cluster of contact fingers 220. The contact fingers 220 are constructed similarly to th se shown in FIGURES 8 and 9, and may be atfixed to, or are integral with, a stationary metal member 224, which also forms a confining outer shell 226. An elastomeric pressure means 228 of annular configuration is disposed between the shell 226 and the back edges of the contact fingers 220. A pressurizing cavity 230 extends annularly within the elastomeric material 228 and communicates with an inlet port 232 for applying a pressurized fluid to the cavity 230 to exert a distributed force within the elastomeric material 228 for producing a quasi-hydrostatic pressure on the contact fingers 220. The contact fingers 220 thus move inward and into intimate contact with the contact rod or bolt, shown in its engaged po ition in dotted line as 222'. Alternatively, the elastomeric material 228 may be pressurized by mechanical means, rather than by the fluid means as shown.

A switch assembly construction having an actuator or actuator mechanism in accordance with a preferred embodiment of the invention will now be described. Although the actuator may comprise merely a simple and suitable mechanical or electrical device for producing a straight and linear motion in the direction of switch closure and opening, such as a piston or low voltage solenoid, this is not necessarily the most desirable construction. The reason for this is that for the longest part of the stroke, very little force is generally required to move the contact assembly. But once the contacts are in engagement, it is desirable, as previously discussed, to apply a high force to achieve the necessary contact pressure. Although this may be achieved in various manners, the mechanism illustrated in FIGURE 7 is advantageous as regards simplicity and reliability.

Generally, means for moving the contact assembly 30 into engagement with the stationary contact and conductor assembly 34 comprises driving means, including the actuator mechanism generally indicated as 33, for applying a relatively low force to initially move the conductive elements or blades 31 into engagement with the contacts 46 and 48, and thereafter applying a relatively high force thereto to establish the hydrostatic-like pressure distribution and uniform and equal contact resistance at each contact point.

More particularly, the stationary electrode assembly 34 is shown securely fastened to a rigd frame by suitably insulated brackets or clamps 80 and 82, each of the conductors 45 and 49 having electrical terminals 83 through 86 attached respectively to their opposite ends. The contact assembly 30 is shown in its engaged or closed position bridging the conductor 45, and being driven and retained in this condition by the actuator mechanism 33.

The movable contact assembly 30 is fastened by any suitable means (not shown) to a pressure plate 88 forming a part of the carriage, indicated generally as 90. An insulating member 91 is interposed between the contact assembly 30 and the plate 88 to insulate the carriage and operating mechanism from the contact assembly. The carriage 90 is supported by links 92a, 92b, as well as 920 and 92d on the opposite side of the carriage 90 and not visible in the figure. The links 92 are pivotally fastened at one of their respective ends to laterally opposite ends of the carriage by means of pins 94a and 94b respectively. The opposite ends of each of the links 92 are pivotally mounted to a fixed frame by means of pins 96a and 96b respectively. Consequently, the carriage 90 and thus the contact assembly 30, is movable into and out of switching engagement, as shown.

A hydraulic or pneumatic mechanism 98 having a cylinder 100 and a piston 102 is disposed generally perpendicular to the direction of carriage motion and drives a connecting rod 104 to an upper and lower position, depending on the pressure at the port 106 to the cylinder. The connecting rod 104 operates a cam 108, which moves the carriage 90 and the contact assembly 30, applying a variable force thereto.

More specifically, the cam 108 is fixedly attached to the upper end of the connecting rod 104 and has a bearing surface 110 parallel thereto (vertical, as shown) which rides on a stationary roller 112 fixed to the frame by means of a bracket 114. Another roller 116 is pivotally fastened by pin 118 to the carriage 90, and functions as a cam-follower, riding along the cam surface 120. The roller 116 is mechanically biased against the cam surface 120 by a spring 121 attached at one end to the pressure plate 88 and at the other end to the frame by a bracket 124. The pivotal axis of roller 116 is desirably colinear with that of roller 112 so that the tangential points of force acting on the cam surfaces are oppositely opposing.

The variable cam surface 120 has generally three parts or portions, the first portion 122 being at the upper end of the cam 120 and receives the follower roller 116 when the connecting rod 104 and piston 102 are in their lower most position (as shown in broken line), wherein the switch is in its open condition. With increasing pressure on the piston 102, the cam 108 is raised so that the follower roller 116 rides on the linear slope 123 which forms the second portion of the camming surface 120. And in the upper most position of the cam, con necting rod and piston, the follower roller 116 rides on the camming surface portion 125 which has a reduced inclination and which diverges downwardly with respect to the opposite vertical bearing surface 110. Thus, in the initial actuation of the switch, the cam 108 moves the carriage and contact assembly through a relatively large distance with relatively small force, and in the final part of the switching action, the carriage and contact assembly is moved a relatively small distance with an extremely large force produced by the wedging action of the inclined camming surface 124 against the rollers 116 and 112.

It is of course understood that the frame to which the mechanism is mounted must be capable of withstanding the contact forces involved, and the entire mechanism may be contained in a single solid integral steel frame.

One example of a switch construction having the capability of carrying 300 kiloamps effectively, utilizes a movable contact assembly having approximately 125 hard copper blades of about inch in width, and a stationary contact formed by bus bars of about 8 inches in width and having contact portions formed by silver strips brazed thereto /a inch wide by inch thick, and having a bus bar gap of about two inches. This switch construction has a pressure element in the form of a rubber cushion having a durometer hardness of 40 to 50. The actuator mechanism provides a total traveling distance of 1.5 inches from closed to open position, and a total contact force of 11,200 pounds.

Although the various embodiments of the contact systems of the present invention are described generally in connection with magnetic forming apparatus, it is of course understood that the present invention, in its various aspects, may be applied to other types of apparatus and uses. As for example, the contact system in accordance with the present invention may be advantageously employed in various welding and other high current apparatus. Furthermore, although the contact systems herein described are generally planar and circular, the principles of the invention are not limited thereto and other geometries or arrangements may of course be constructed employing the teachings of the present invention.

Various modifications of the embodiments disclosed herein will be apparent to those skilled in the art, and as such, the scope of the invention should be defined only by the claims, and equivalents thereof.

Various features of the invention are set forth in the following claims.

What is claimed is:

1. A contact system comprising an assembly having a plurality of conductor elements, a contact adapted to be engaged by said plurality of conductor elements, means for driving said plurality of conductor elements and said contact into engagement to form parallel conductive paths at points between each of said plurality of conductor elements and said contact, said assembly comprising forcedistributing means responsive to the force produced by said driving means, and pressure means responsive to said force-distributing means providing hydrostatic-like pressure on said plurality of conductor elements, applying an equal pressure to each element so that equalization of contact resistance is produced at each contact point when said plurality of conductor elements are in engagement with said contact.

2. The contact System of claim 1 wherein said forcedistributing means comprises a rigid member in mechanical contact with said pressure means.

3. The contact system of claim 1 wherein said means for producing hydrostatic-like pressure comprises a volume of elastomeric material, means confining said material against said plurality of conductor elements and means for applying a. substantially high force to substantially all of said material.

4. The contact system of claim 3 wherein said elastomeric material comprises at least two layers, one layer disposed adjacent said conductive elements and being relatively hard, and another layer spaced from said plurality of conductor elements and being relatively soft.

5. The contact system of claim 3 wherein said elastomeric material has at least two surfaces, one of which engages said plurality of conductor elements, and the other of which engages a surface portion of said confining means having a surface configuration corresponding to the adjacent surface of said elastomeric material.

6. The contact system of claim wherein said other surface of the elastomeric material is bonded to said surface portion of said confining means.

7. The contact system of claim 5 wherein said one surface of the elastomeric material is bonded to each of said plurality of conductor elements at one end thereof.

8. The contact system of claim 5 wherein both of said surfaces of the elastorneric material are generally parallel.

9. The contact system of claim 5 wherein said surface portion of the confining means and said adjacent surface of said elastorneric material are planar.

10. The contact system of claim 1 wherein said means for generating hydrostatic-like pressure comprises a hydrostatic chamber filled with relatively non-compressible fluid, and having a resilient wall in engagement with said plurality of conductor elements at one end thereof, and means for applying a force to said chamber in the direction producing contact engagement.

11. The contact system of claim 10 wherein the hydrostatic chamber has a flexible wall surrounding the entire volume of said non-compressible fluid.

12. The contact system of claim 1 wherein said forcedistributing means comprises a pressurized fluid acting on said pressure means.

13. The contact system of claim 3 wherein said plurality of conductor elements are arranged in a closed geometrical configuration.

14. The contact system of claim 13 wherein said closed geometrical configuration is a circle and said elastorneric material fills the center cavity thereof so as to exert an outward quasi-hydrostatic pressure on said plurality of conductor elements in response to said force-distributing means.

15. The contact system of claim 13 wherein said closed geometrical configuration is a circle and said elastorneric material is disposed between the periphery of the plurality of conductor elements and said confining means so as to exert an inward quasi-hydrostatic pressure on said plurality of conductor elements in response to said forcedistributing means.

16. The contact system of claim 1 wherein each of said plurality of conductor elements has a planar configuration, each being parallelly disposed to the other, and having the corresponding edges of each constituting at least a portion of the contact area of the contact system.

17. The contact system of claim 1 wherein said contact comprises a planar conductive element, said contact system further comprising a further planar conductive element for the conduction of current of the opposite polarity from that of the contact spaced from said first planar element, and an insulator disposed therebetween.

18. The contact system of claim 1 wherein said means for moving said contact assembly comprises driving means for applying a relatively low force to move the plurality of conductor elements into engagement with said contact, and thereafter for applying a relatively high force thereto.

19. The contact system of claim 18 wherein said driving means comprises a variable force convertor and means for supplying a substantially constant force thereto.

20. The contact system of claim 18 wherein said means for moving the contact assembly comprises carriage means attached to said assembly and pivotally mounted to a fixed frame, reciprocating driving means attached to a fixed frame and having first and second positions, cam and follower means associated with the carriage means and reciprocating driving means for applying a variable force to said contact assembly as said driving means is moved from said first position to said second position.

21. A contact system comprising an assembly having a plurality of conductor elements adapted to engage a pair of contacts to form a conductive bridge thereacross, forming parallel conductive paths at points between each of said plurality of conductor elements and each contact, said assembly comprising force-distributing means adapted to receive a force applied thereto, and pressure means responsive to said force-distributing means for providing hydrostatic-like pressure on said plurality of conductor elements, applying an equal pressure to each of said plurality of conductor elements so that equalization of contact resistance is produced at each contact point when said plurality of conductor elements are in engagement With said contacts.

22. The contact system of claim 21 wherein said pressure means comprises an elastorneric material, said material having substantially its entire surface area confined.

23. The contact system of claim 21 wherein said pressure means comprises elastorneric material having at least two surfaces, and said force-distributing means comprises a rigid member abutting against substantially the entire area of one of said surfaces, and the other of said surfaces being pressed against said plurality of conductor elements.

References Cited UNITED STATES PATENTS 1,978,246 10/ 1934 Bauerschmidt. 2,639,355 5/1953 Dunsheath. 3,180,960 4/1965 Barkan et al. 3,201,556 8/1965 Baird.

HERMAN O. JONES, Primary Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,487 ,456 Dated Dec 3O 1969 Inventor(s) Paul Wildi It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 13 "pressure" should be pressures Column 6, line 37 "200" should be 220 Claim 1, column 8, line 47, after the comma insert me,ans associated with said forcedistributing means constraining said plurality of conductor elements to said assembly while permitting said elements to be freely movable relative to each other in the direction to produce said engagement,--.

Claim 21, column 10, line 26, after the comma insert means associated with said forcedistributing means constraining said plurality of conductor elements to said assembly while permitting said elements to be freely movable relative to each other in the direction to produce contact engagement,--.

SI'GNF AND SFMED Aunt:

Edward M. mean. Ir. mm: x. m. Oomissiom 0: Patents FORM Pia-1050 (10-691 uscoMM-Dc man-Pea i .5, GOVERNMENT FItNTlIIG OFFICE llil 0-30. 8 

